Layered catalysts, such as transition metal catalysts, are well known catalysts that have a wide range of applications. For example, transition metal catalysts are useful in hydrotreating petroleum feedstocks to remove heteroatoms in the feed, like sulfur, oxygen and nitrogen, and transition metal catalysts can be used in hydrogenation processes, alcohol synthesis from syngas, hydrodemetallization of heavy crudes, catalytic hydrovisbreaking and the like.
The activity and, indeed, the selectivity of transition metal sulfide catalysts vary widely. However, achievement of multiple product targets can cause problems. For example, there has been a wide variety of sulfur containing molybdenum and tungsten catalysts that have been reported as useful in hydroprocessing petroleum feedstocks containing heteroatoms such as sulfur, oxygen and nitrogen. Because these catalysts display differences in selectivity, it has been generally necessary in hydrotreating these heteroatom containing petroleum feedstocks to overtreat the feedstock in order to obtain a treated product having a predetermined sulfur and nitrogen content. For example, it may be necessary to remove more nitrogen than is necessary to obtain a product with the desired sulfur content. This is particularly disadvantageous because it does not permit precise control over the sulfur and nitrogen levels in the treated product. It is also economically undesirable because of the excess hydrogen consumed in overtreating the feed, as well as the increased time and energy expended in achieving the desired product composition. Thus, there remains a need to improve transition metal catalyzed hydrotreating processes whereby a predetermined level of reduction of sulfur and nitrogen in the feedstock can be achieved with greater efficiency and/or less hydrogen consumption.